MadSci Network: General Biology |
The following paragraph is from an enzyme web site (http://www.facstaff.bucknell.edu/toner/gb/lab121/labs34.html) but it explains the relationship between enzyme activity and temperature very well: --------------------------------------------------------------------------- All chemical reactions speed up as temperature is raised. As the temperature increases, more molecules have enough kinetic energy to undergo the reaction. Since enzymes are catalysts for chemical reactions, enzyme reactions also tend to proceed faster with increasing temperature. However, if the temperature of an enzyme-catalyzed reaction is raised still further, an optimum is reached: above this point, the kinetic energy of the enzyme and water molecules is so great that the structure of the enzyme molecules starts to be disrupted. The positive effect of speeding up the reaction is now more than offset by the negative effect of denaturing more and more enzyme molecules. Many proteins are denatured by temperatures around 40-50deg.C, but some are still active at 70-80deg.C, and a few even withstand being boiled. --------------------------------------------------------------------------- Different enzymes have different optimum temperatures, depending on the organism and environment they have evolved in. The same enzyme can also have different optimum temperatures depending on it's source. As an example, I found the following reference for a plant catalase that has an optimum temperature of 40 deg. C and an operating range of 0-50 deg. C. --------------------------------------------------------------------------- TITLE: One-step purification and properties of catalase from leaves of Zantedeschia aethiopica. AUTHORS: Trindade H; Karmali A; Pais MS AUTHOR AFFILIATION: Falcudade de Ciencias de Lisboa, Departamento de Biologica Vegetal, Lisbon, Portugal. SOURCE: Biochimie 1988 Dec;70(12):1759-64 ABSTRACT: Catalase (E.C 1.11.1.6) was purified from leaves of Zandedeschia aethiopica to apparent hmogeneity by a one-step hydrophobic interaction chromatography on a phenyl Sepharose CL-4B column. The purified enzyme preparation was obtained with a final recovery of enzyme activity of about 61% and a specific activity of 146 U/mg protein. The purified enzyme ran as a single protein band when analyzed both by native PAGE and SDS-PAGE corresponding to an Mr of 220,000 Da, which consists of 4 subunits with identical Mr of 54,000 Da. The pI of purified enzyme was found to be 5.2 by isoelectric focusing on ultrathin polyacrylamide gels. The purified catalase has an optimum temperature of activity at 40 degrees C, whereas it is stable between 0 degrees and 50 degrees C. As regards pH, the enzyme has an optimum activity at pH 7.0 and it is stable in the range pH 6-8. The absorption spectrum of the purified enzyme exhibited 2 peaks at 280 nm and 405 nm. CAS REGISTRY NUMBERS: EC 1.11.1.6 (Catalase) --------------------------------------------------------------------------- So there is no single answer to your question! Depending on the particular catalase you're interested in, you will find different optimum temperatures. Hope this helps!
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